See
http://www.flightglobal.com/articles/20 ... tware.html" onclick="window.open(this.href);return false; for full story and pictures explaining why and how "finger trouble" can lead to rather "interesting takeoffs" (or rejected ones)...
DATE:16/03/10
SOURCE:Air Transport Intelligence news
FAA: Rejected takeoffs necessitate Boeing 777 software change
By John Croft
The US FAA tomorrow will issue a final airworthiness directive calling on operators of more than 800 US-registered Boeing 777s to update the software in the aircraft's three autopilot flight director computers by the end of June to prevent possible rejected takeoffs (RTOs) and poor single-engine climb performance.
The FAA says in January alone there were two rejected takeoffs for Boeing 777s at speeds "above takeoff decision speed following inadvertent engagement of the autopilot on the ground", adding to the seven other reported rejected takeoff cases since 1995.
With the autopilot engaged on the ground, the pilots feel higher than normal control forces when they attempt to pull the control column aft at takeoff speed, a surprise sensation that can lead to a high-speed abort.
"This condition, if not corrected, could result in rejected takeoff at rotation speed, and consequent possible overrun of the runway," says the FAA in the airworthiness directive (AD), to be published 17 March.
Boeing on 22 January issued a service bulletin to operators of all 777 models built before line number 819 giving operators one year to update the autopilot flight director computer (AFDC) software.
"Inadvertent engagements of the autopilot while the airplane is on the ground are rare events," Boeing says. "During its 15-year service history, the 777 fleet has accumulated more than 4.8 million flights and there have been just nine reported instances of a rejected takeoff because of inadvertent engagement of the autopilot. There have been no runway overruns or injuries associated with these RTOs."
The new software version inhibits the autopilot from being engaged when the aircraft is below 50ft (15m) or if its flaps are extended. During the ground portion, the new software will disengage the autopilot if for some reason it is turned on when the aircraft is on the ground with flaps extended but not in the rollout mode associated with the auto-land function.
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